Multi-component application systems have been used, for example, in manufacturing plastic articles by applying resinous materials to a mold or perform for an article, or to pre-arranged fiber reinforcing materials, or with fiber reinforcing materials as they are being applied.
In multi-component application systems, a liquid resin and a curing agent for the resin are most generally mixed and dispensed into molds or onto articles or preformed substrates where the curing agent and resin react and harden. In spraying applications, the resin and curing agent components are mixed together, either externally or internally of the apparatus, and the mixture is directed onto a substrate, such as a preform, as a plural component spray.
In internal mix systems, the resin and catalyst are mixed within the spraying apparatus, and the mixture is then dispensed by a nozzle and directed onto the substrate. Complete and thorough mixing of the resin and catalyst is vital to avoid non-uniform hardening of the resin on the substrate and other undesirable results. Furthermore, mixed resin and catalyst must be removed from an internal mix apparatus to avoid blockage of the apparatus by cured resin, and such apparatus are generally flushed with flows of compressed air and/or solvent to prevent such blockage.
U.S. Pat. No. 3,799,403 discloses an internal mix dispensing apparatus including a mixing chamber that is movable with respect to the housing of the device. In the disclosed apparatus, moving the mixing chamber to the mix position causes the components of the plural component material to be introduced into the mixing chamber, appropriately mixed and then dispensed; and thereafter moving the mixing chamber to the purge position terminates the introduction of components into the mixing chamber and introduces compressed air into the mixing chamber to substantially purge residue component material from the mixing chamber and its cooperatively associated orifice. In addition, the compressed air can be employed during the dispensing of the mixture of component materials of the plural component material so as to assist in atomizing particles of the material from the terminus of the mixture of plural component material as such material is ejected from the orifice of the device and to assist in shaping the spray pattern of the plural component material particles.
In spraying systems using compressed air, the quantity of air used and its substantially controllable expansion in the workplace can create problems. It is expensive to compress air, and the large quantities of compressed air used by existing systems can impose a significant operating cost on the system. In addition, the blast of compressed air used to atomize liquid components carries a significant quantity of spray particles away from the substrate, wastes the expensive material, creates an unclean spray area, contributes to the problem of operating such manufacturing operations safely and frequently requires overspray collection systems. Furthermore, the use of large quantities of air during operation of the system can often create an undesirable spread of fumes, and create a problem in meeting environmental standards.
In addition, in internal mix dispensers, the failure and wear of internal seals and improper maintenance can result in mixed plural component materials, such as polyester resins, hardening within the dispensing apparatus and requiring its disassembly and repair before it can be satisfactorily operated again.